Have you ever been told that Transitions lenses need to be put into the freezer in order to be “Activated”? This myth just doesn’t seem to go away. I first heard it about fifteen years ago, when one of my customers had asked me if their new Transitions lenses needed to be put in the freezer overnight in order to be activated. I thought it sounded a little strange, but I checked it out and discovered it was not true. I can’t remember the last time I got this question in my store, but I began thinking about it recently and a quick google search revealed a blog post with lots of comments from glasses wearers reporting that their optician had actually instructed them to “activate” their new Transitions lenses by putting them in the freezer overnight. Wait, what? There are opticians out there responsible for spreading this myth. No wonder it is still around.
So why does this belief persist? To answer that question, we first need to understand the science of how Transitions lenses work. There are trillions of photochromic molecules in the lenses that change structure when exposed to UV light. This change in structure is what causes the lenses to darken in sunlight. They are constantly restructuring themselves based on the amount of UV light they are exposed to, which changes continuously as you move about from indoors to outdoors and through shaded and non-shaded areas. This technology is wonderful for protecting your eyes from harmful UV and blue light both indoors and out.
The Effect of Temperature
When it is colder outside you may notice that your Transitions lenses seem to get darker than they do when it is warmer. This is because the molecules move more slowly when they are cold, which means when they are cold they will fade back from dark to clear more slowly. If you move into a shaded area outdoors, they will stay darker longer than they would on a warm day. When you move into a shaded area when the temperature is warm outside, the molecules will be quicker to respond to the reduced UV and they will begin to lighten up more quickly. I believe people have noticed this effect that cold temperatures have on the lenses, and then some of these people have made the leap to believing that placing a new set of Transitions lenses into the freezer overnight is needed to activate them. It is important to understand that temperature does have an effect on the lenses, but simply freezing them does not change them permanently. When they are colder they fade back slower, and when they are warmer they fade back faster. So now you know, and if you were one of those who believed the myth, now you can stop putting your lenses in your freezer. Save it for your ice-cream and frozen veggies.